ATBECHDEDKESFRGBGRITLILUNLSEMCPTIESILTLVFIROMKCYALTRBGCZEEHUPLSK..HRIS..MTNORS..SM..................*J2.0.21 - 2100000/03551684EUROPEAN PATENT SPECIFICATIONB120230329EP17826630.0201712122019062120200409enenen201662432798 P20161212US20230329202313201910162019422023032920231320230104C08G 59/18 20060101AFI20180622BHEP C08G 59/40 20060101ALI20180622BHEP C08G 59/42 20060101ALI20180622BHEP C08G 59/68 20060101ALI20180622BHEP C08G 59/42 20130101 FI20180320BHEP C08G 59/4215 20130101 LI20180802BHEP C08G 59/68 20130101 LI20180320BHEP deNEUARTIGE, BEI NIEDRIGEN TEMPERATUREN GEHÄRTETE ANHYDRIDEPOXIDSYSTEMEenNOVEL LOW TEMPERATURE ANHYDRIDE EPOXY CURED SYSTEMSfrNOUVEAUX SYSTÈMES ÉPOXY DURCIS PAR ANHYDRIDE À BASSE TEMPÉRATUREEP-A1- 0 615 994WO-A1-2009/089145WO-A1-2014/165423JP-A- 2005 075 915US-A- 3 329 652PATEL, Pritesh G.8577 Ash LaneBreinigsville, PA 18031USLAL, Gauri Sankar1951 Pierce DriveWhitehall, PA 18052USLA COMARE, Douglas M.1329 Kingston CourtNorthampton, PA 18067USEvonik Operations GmbH1018436372016P14013WERellinghauser Straße 1-1145128 EssenDEEvonik Patent Association101801622c/o Evonik Industries AG IP Management Bau 1042A/PB 15 Paul-Baumann-Straße 145772 MarlDEALATBEBGCHCYCZDEDKEEESFIFRGBGRHRHUIEISITLILTLULVMCMKMTNLNOPLPTRORSSESISKSMTRUS201706583320171212enWO201811188420180621201825 BACKGROUND OF THE INVENTION

Anhydrides have been used as curing agents for epoxy resins since the mid-1960s. Initially there were twelve such compounds in commercial use. They possess the advantage of producing only mild skin irritation compared to amine curing agents and generally provide low viscosity and long pot life. Cured epoxy resins from anhydrides generally exhibit high temperature stability, good radiation stability as well as improved physical and electrical properties above their deflection temperature (DT). Chemical resistance to some reagents is less than with amine-cured systems, but is better against aqueous acids. As a result, epoxy-resin cured with anhydrides have been extensively used as electrical insulating materials. Anhydrides require more severe curing conditions than amine-based curing agents but are suitable for making large moldings, as they have a long pot life and form cured resins having relatively well-balanced electrical, chemical, and mechanical properties while generating a small quantity of heat. Anhydrides have been widely used as curing agents for epoxy resins for structural composite and electrical potting applications for several decades. The reaction of anhydrides with resins are dependent on a number of factors including the gel time and temperature, post-cure and post cure temperature, presence or absence of accelerators, type of accelerator, amount of hydroxyl group in the resin, ratio of anhydride to epoxy and the amount of free acid in the system. Anhydrides will not react with epoxy groups in the absence of an accelerator. Hydroxyl group from the resin or from added alcohols can catalyze the reaction but the reaction is generally slow.

Almost all commercial epoxy-resin/anhydride formulations use anhydride accelerators. These are acidic or basic compounds. Acids favor etherification while bases favor esterification. The optimum anhydride/epoxy ratio (A/E) and the cured properties of the resin are determined by the accelerator used. Tertiary amines are conventionally used as anhydride accelerators. These are described in Three Bond Technical News vol. 32, Dec 20, 1990. They include benzyldimethylamine (BDMA) and tris(dimethylaminomethyl)phenol, triethylenediamine (TEDA), N,N-dimethylpiperazine and 2-(dimethylaminomethyl)phenol. Imidazoles such as 2-methylimidazole, 2-ethyl-4-methylimidazole,1-cyanoethyl-2-undecylimidazolium trimellitate and the epoxy-imidazole adduct (2-methylimidazole/Epon 828) have also been used.

US 3,839,281describes the use of N-hydroxyethyl piperidines and piperazyl compounds as accelerators for epoxy resins systems cured with anhydrides and dicyandiamide (DICY). In US 5,650,477 quaternary ammonium salts bearing an ether linkage with a nitrile group were used as catalysts for anhydride cured epoxy resins under microwave irradiation. Solid metal acetylacetonates are described as latent curing agents in J. Appl. Poly. Sci, 26, 1981, 979 by J. Smith. These solids have the disadvantage of not being able to be dispersed adequately to effect efficient curing of epoxy resins by anhydrides. In WO 2013009452 A1, the anhydride epoxy system was cured at 80°C for 3 h to obtain 90% conversion. The publication discloses the use of a standard epoxy: anhydride ratio. WO 2009/089145 A1 discloses a thermoset resin comprising the reaction product of an epoxy resin mixture, a cycloaliphatic anhydride hardener and a catalyst. The catalyst can be, among others, a tertiary amine or an imidazole. The catalyst can be present in amounts of up to 10 weight percent, and the anhydride hardener in amounts of 35 to 65 weight percent. US 3,329,652 A discloses a process of curing polyepoxides with at least 0.5 equivalents polycarbocylic acid anhydride and from 0,1 to 10 weight percent of the polyepoxide of an imidazole salt.
JP 2005 075915 A discloses an anhydride based curing agent and an amine-based tertiary amine-based curing accelerator with a weight ratio of anhydride to tertiary amine-based curing accelerator from 100 : 0.1 - 5. EP 0 615 994 A1 discloses an epoxy resin composition comprising an epoxy resin, an acid anhydride and least one of a latent curing accelerator and a dispersible latent curing accelerator. The ratio of epoxy resin to anhydride is from 0.8 to 1.2 based on the equivalents, and the amount of both curing accelerators is each from 0.1 to 10 parts by weight based on the epoxy resin. WO 2014/165423 A1 discloses a composition comprising at least one tertiary amine salt and at least one epoxy resin and optionally at least one DICY.

In the current system used for anhydride cured systems the following conditions are utilized:

  1. (1) Anhydride to epoxy resin ratio is usually 1: ~1 (molar ratio)
  2. (2) Typical accelerator usage is 1-3% with active accelerators (not stable in anhydride at greater loading)
  3. (3) Temperature of cure is ~150°C for >4 h

The major limitation of anhydrides as curing agents for epoxy resin is the fact that they require high cure temperature (>150°C) for several hours (>4 h). Also the cured products possess poor hot wet properties which limit their use in an application in hot and wet environments. Typically anhydride active accelerators such as benzyldimethylamine (BDMA) and tris(dimethylaminomethyl)phenol (DMP-30, K54), triethylenediamine (TEDA), N,N-dimethylpiperazine and 2-(dimethylaminomethyl)phenol cannot be pre-blended at higher loading in anhydride formulation due to their rapid opening of the anhydride ring. This results in gelation in absence of epoxy resin during storage. There is a need for tertiary amine based anhydride accelerators with longer latency than the current materials in order to minimize the waste of the pre-mixed anhydride system thereby providing a significant saving in raw material cost. These latent anhydride accelerators should exhibit prolonged storage stability in admixture with anhydride curing agents and epoxy resins at ambient temperature cure. In addition, they should reduce the cycle time and thereby provide increased throughput. Furthermore, a reduction of cure temperature is necessary for lower energy use during processing as well as the reduction of hot-spots and embrittlement in the cured product. Herein we describe a new anhydride curing system which has solved most of the problems inherent in the current curing systems.

BRIEF SUMMARY OF THE INVENTION

The invention is a curing agent composition for epoxy resin comprising anhydride and approximately equimolar amount of tertiary amine or an imidazole and carboxylic acid wherein the weight ratio of anhydride to combined tertiary amine or imidazole and carboxylic acid is 50:50. The composition of this invention uses a lower ratio of epoxy resin to anhydride (1: 0.4-0.6) than typically used (1: 0.8-1.1). In addition, it uses a higher loading of a hindered latent tertiary amine or an imidazole in combination with a carboxylic acid (wt% ratio of combined amine and carboxylic acid to anhydride -10%). With this formulated system a full cure can be achieved in less than 2 h at a significantly lower temperature (~100°C).

The amine used for this invention is 1-piperidinylethanol (N-hydroxyethylpiperidine, NHEP) represented by the structure below or an imidazole represented by the structure below: Imidazole: R1 = H, a C1-C20 straight chain or branched alkyl, or a monocyclic aryl; R2 = a C1-C20 straight chain or branched alkyl, or a monocyclic aryl.

The carboxylic acid is represented by RCOOH; R= a C1-C20 straight chain or branched alkyl, or a monocyclic aryl.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a graph showing the Tg (°C) for different ratios of epoxy to anhydride (Phr) packages.

DETAILED DESCRIPTION OF THE INVENTION

In order to overcome the above limitations, we have found that when the anhydride formulation contains approximately 10% of the N-hydroxyethylpiperidine (NHEP) or imidazole salts based liquid latent accelerator and the ratio of epoxy to anhydride is significantly lower than conventional (1:0.8-1) vs. ours (1:0.4-0.6), the full conversion of the formulation can be achieved at 100°C in <2 h. These conditions give the optimum cured performance to meet the structural processing and application needs. For this concept we have used methylhexahydrophthalic anhydride (MHHPA) and nadic methyl anhydride (NMA). However, this can be applied to other mono and di-carboxylic acid anhydrides that are used in industry to cure epoxy resins.

Representative carboxylic acids are acetic acid, propanoic acid, hexanoic acid, 2-ethyl-hexanoic acid, decanoic acid, tall oil fatty acid (TOFA), as well as a dicarboxylic or tricarboxylic acid. For a dicarboxylic acid two mole equivalents of the amine is used with one mole equivalent of the acid while with tricarboxylic acid three mole equivalents of the amine with one equivalent of the acid.

These catalysts may be used in a composition consisting of an anhydride curing agent and an epoxy resin. Suitable epoxy resins include the following:

Epoxy resins commercially available under the trade name DER 383 (available from Dow) and EPON 826 (available from Hexion Specialty Chemicals) are suitable for this application.

Other epoxy resins may include, but are not limited to, bi-functional epoxies, such as, bisphenol-A and bisphenol-F resins. Multifunctional epoxy resin, as utilized herein, describes compounds containing two or more 1,2-epoxy groups per molecule. Epoxide compounds of this type are well known to those of skill in the art and are described in Y. Tanaka, "Synthesis and Characteristics of Epoxides", in C. A. May, ed., Epoxy Resins Chemistry and Technology (Marcel Dekker, 1988), which is incorporated herein by reference.

One class of epoxy resins suitable for use in the present disclosure comprises the glycidyl ethers of polyhydric phenols, including the glycidyl ethers of dihydric phenols. Illustrative examples include, but are not limited to, the glycidyl ethers of resorcinol, hydroquinone, bis-(4-hydroxy-3,5-difluorophenyl)-methane, 1,1-bis-(4-hydroxyphenyl)-ethane, 2,2-bis-(4-hydroxy-3-methylphenyl)-propane, 2,2-bis-(4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis-(4-hydroxyphenyl)-propane (commercially known as bisphenol A), bis-(4-hydroxyphenyl)-methane (commercially known as bisphenol-F, and which may contain varying amounts of 2-hydroxyphenyl isomers), and the like, or any combination thereof. Additionally, advanced dihydric phenols of the following structure also are useful in the present disclosure: where m is an integer, and R is a divalent hydrocarbon radical of a dihydric phenol, such as those dihydric phenols listed above. Materials according to this formula can be prepared by polymerizing mixtures of a dihydric phenol and epichlorohydrin, or by advancing a mixture of a diglycidyl ether of the dihydric phenol and the dihydric phenol. While in any given molecule the value of m is an integer, the materials are invariably mixtures which can be characterized by an average value of m which is not necessarily a whole number. Polymeric materials with an average value of m between 0 and about 7 can be used in one aspect of the present disclosure. In other embodiments, the epoxy component may be a polyglycidyl amine from one or more of 2,2'-methylene dianiline, m-xylene dianiline, hydantoin, and isocyanate.

The epoxy component may be a cycloaliphatic (alicyclic) epoxide. Examples of suitable cycloaliphatic epoxides include diepoxides of cycloaliphatic esters of dicarboxylic acids such as bis(3,4-epoxycyclohexylmethyl)oxalate, bis(3,4-epoxycyclohexylmethyl)adipate, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate, vinylcyclohexene diepoxides; limonene diepoxide; bis(3,4-epoxycyclohexylmethyl)pimelate; dicyclopentadiene diepoxide; and other suitable cycloaliphatic epoxides. Other suitable diepoxides of cycloaliphatic esters of dicarboxylic acids are described, for example, in WO 2009/089145 A1, which is hereby incorporated by reference.

Other cycloaliphatic epoxides include 3,3-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate; 3,3-epoxy-1-methylcyclohexyl-methyl-3,4-epoxy-1-methylcyclohexane carboxylate; 6-methyl-3,4-epoxycyclohexylmethylmethyl-6-methyl-3,4-epoxycyclohexane carboxylate; 3,4-epoxy-2-methylcyclohexyl-methyl-3,4-epoxy-3-methylcyclohexane carboxylate. Other suitable 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylates are described, for example, in U.S. Patent No. 2,890,194, which is hereby incorporated by reference. In other embodiments, the epoxy component may include polyol polyglycidyl ether from polyethylene glycol, polypropylene glycol or polytetrahydrofuran or combinations thereof.

Suitable anhydrides include linear polymeric anhydrides such as polysebacic and polyazelaic anhydride. Alicyclic anhydrides such as methyltetrahydrophthalic anhydride (MTHPA), tetrahydrophthalic anhydride, nadic methyl anhydride (NMA), hexahydrophthalic anhydride (HHPA), and methylhexahydrophthalic anhydride (MHHPA). Simple alicyclic anhydrides such as succinic anhydride, substituted succinic anhydride, citric acid anhydride, maleic anhydride and special adducts of maleic anhydride, dodecyl succinic anhydride, dodecenylsuccinic anhydride (DDSA), maleic anhydride vinyl and styrene copolymers of maleic anhydride, multi-ring alicyclic anhydrides and aromatic anhydride such as phthalic anhydride and trimellitic anhydride.

The compositions of this invention may contain from about 0.4 to about 0.6 equivalents of anhydride curing agents per equivalent of epoxy and preferably from 0.5 to 0.6 equivalents. The accelerator may suitably be employed in a ratio of about 1-40 parts per hundred parts of curing agent. In another embodiment, the accelerator may suitably be employed in a ratio of about 1-20 parts per hundred parts of curing agent. In yet another embodiment, the accelerator may suitably be employed in a ratio of about 1-10 parts per hundred parts of curing agent. In contrast to standard epoxy:anhydride ratio (1:0.8-1), which is commonly used in such formulations for structural laminates and composites applications, the proposed approach only contains 0.4 - 0.6 part of anhydride curing agent to 1 part of epoxy resin.

The advantages we believe this technology would bring are as follows:

  1. 1) It will allow fabricators to lower the cure temperature and time (150°C for 6 hrs to 100°C for 2 hrs) for applications such as Pultrusion.
  2. 2) Minimize or eliminate the failure of anhydride formulation under a cyclic load due to micro stress when it is cured at lower temp (100°C) for VARTM- syntactic.
  3. 3) Improve overall EH&S performance in contrast to where amines are used.
  4. 4) Provide a new formulating tool to offer where long pot life low exotherm is required.

Aspects of the present invention are, for example, as follows

Examples Example 1 (not inventive)

General procedure for preparation of a low temperature anhydride cure system.

The novel low temperature cure system was prepared by adding NHEP (19 gms) and cyclohexanedimethyl amine (28 gms) into a 3-neck round bottom flask equipped with an overhead mechanical stirrer and nitrogen inlet and thermocouple. The ethyhexanoic acid (58 gms) was added slowly to maintain the temperature at 25-30°C for 1 hour. Once salt is formed, methylhexahydrophthalic anhydride (MHHPA) (900 gms) was added slowly to maintain the temp. ~25-30°C over a period of 30 mins. On completion, epoxy (2000 gms) was added at room temperature and the whole mixture was stirred for 10 mins to make low temperature anhydride system. Thermal study was conducted using DSC to understand the cure kinetics, reactivity and Tg. Latency study was determined using Brookfield viscometer with Wingather software to generate viscosity cure profile. The mechanical properties such as tensile, flexural and compression were tested according to ASTM methods using Instron machine.

Example 2 (not inventive)

General procedure for preparation of a low temperature anhydride cure system.

The novel low temperature cure system was prepared by adding Imidazole (32 gms) into a 3-neck round bottom flask equipped with an overhead mechanical stirrer and nitrogen inlet and thermocouple. The octanoic acid (68 gms) was added slowly to maintain the temperature at 25-30°C for 1 hour. Once salt is formed, methylhexahydrophthalic anhydride (MHHPA) (900 gms) was added slowly to maintain the temp. ~25-30°C over a period of 30 mins. On completion, epoxy (2000 or 2250 gms) was added at room temperature and the whole mixture was stirred for 10 mins to make low temperature anhydride system. Thermal study was conducted using DSC to understand the cure kinetics, reactivity and Tg. Latency study was determined using Brookfield viscometer with Wingather software to generate viscosity cure profile. The mechanical properties such as tensile, flexural and compression were tested according to ASTM methods using Instron machine.

Example 3 (not inventive)

The novel low temperature cure systems were prepared by adding 1-methyl imidazole (AMI-1) (36.44 gms) into a 3-neck round bottom flask equipped with an overhead mechanical stirrer and nitrogen inlet and thermocouple. The octanoic acid (63.66 gms) was added slowly to maintain the temperature at 25-30°C for 1 hour. Once salt was formed, the anhydride (MHHPA) (900 gms) was added slowly to maintain the temp. ~25-30°C over a period of 30 mins. On completion, epoxy (2250 gms) was added at room temperature and the whole mixture was stirred for 10 mins to make low temperature anhydride system. Thermal study was conducted using DSC to understand the cure kinetics, reactivity and Tg. Latency study was determined using Brookfield viscometer with Wingather software to generate viscosity cure profile. The mechanical properties such as tensile, flexural and compression were tested according to ASTM methods using Instron machine.

Differential Scanning calorimetric (DSC) study of anhydride accelerators

The methylhexahydrophthalic anhydride (54g) (containing the anhydride accelerator) and bisphenol A diglycidyl ether resin (100g) were mixed using a stainless steel spatula until a uniform mixture was obtained. A sample of this mixture was analyzed by DSC (TA Instruments QA20) using a program that starts at 250C and heats at 100C/minute up to 3000C, cools and scans a second time to 2500C. The first scan provides cure data including onset temperature, peak exotherm and heat of reaction, while the second scan confirms the glass transition temperature.

Example 4 Latency study of anhydride accelerators

The salts prepared in example 1 were analyzed for latency. Pot life of each system was measured by Brookfield viscometer which was connected to a laptop computer using the Brookfield Wingather program. The viscosity versus time and temperature were recorded. Table 1 Isothermal DSC (° C) Formulation phr cure schedule onset peak heat of rxn Tg ° C time to 10K (mins) time to 250K (mins) 90:10* MHHPA:A2910 80 65C-2hrs 103 132 193.9 111 ND ND 80:20* MHHPA:A2910 80 65C-2hrs 87 127 106.7 84 ND ND 70:30* MHHPA:A2910 80 65C-2hrs 90 125 50.9 62 ND ND 60:40* MHHPA:A2910 80 65C-2hrs 86 132 36.11 44 ND ND 50:50 MHHPA:A2910 80 65C-2hrs 120 121 39.72 25 ND ND = not inventive
ND: No Data & NO : Not observe
A2910 - Ancam ine A2910
Ancamine is a registered trademark of Evonik Corp.

The purpose of this experiment was to understand the cure conversion at lower temp and optimum Tg of the cure material. In order to achieve complete cure at lower temp. (65C -2 hrs) the above formulations were prepared to study the effect of cure conversion using Isothermal DSC. The anhydride to accelerator loading was varied from 90:10 - 50:50. The typical phr for epoxy anhydride used was 100:80. The results of DSC shows that there was residual heat of reaction for each combination in Table 1 which is an indication of incomplete cure. The conclusion of this experiment was cure temp. should be higher than 65C. It is worthy of note that the accelerator used for this concept allows use at higher loading without impacting physical form (e.g. viscosity) of curing package. e.g. other accelerators for anhydride epoxy cure cannot be used > 5% in the anhydride. At higher loading these accelerators (e.g. K-54, A1 110, BDMA, Lindax-1) cause instability of the curing agent formulation and result in a rapid buildup in viscosity in absence of epoxy resin. Table 2 Isothermal DSC (° C) Formulations Phr Cure schedule Onset Peak Heat of rxn Tg ° C Time to 10K(mins) Time to 250K (mins) 90:10* MHHPA:A2910 80 100C-2hrs 122 139 19.91 116/113 ND ND 80:20* MHHPA:A2910 80 100C-2hrs 114 146 6.32 100/85 ND ND = not inventive

The second experiment was conducted at a higher temp. 100C and cure time was kept the same to understand the effect of temp. on cure conversion and Tgs. The results of DSC are shown in Table 2. The Tg was improved when cured at higher temp (100C), however there was still residual exotherm observed which indicated cure was not complete. It is important to achieve complete cure in order to obtain cured product that is stable to high temperature, water and other chemicals. Latter conditions result in deterioration of the cure network that result in failure of the cure product during its service. Table 3 Isothermal DSC (° C) Formulations Phr Cure schedule Onset Peak Heat of rxn Tg° C Time to 10K (mins) Time to 250K (mins) 90:10* MHHPA:A2910 60 100C-2hrs NO NO NO 103/108 545 905 80:20* MHHPA:A2910 60 100C-2hrs NO NO NO 91/98 211 415 = not inventive

In the third experiment, the stoichiometry of the anhydride curing package relative to epoxy resins was changed from 1:0.8 to 1:0.6 to check if complete cure can be obtained having less amount of curing agent. As shown in Table 3, lesser amount of curing agent (0.6) resulted in full conversion of formulation when cured at 100C for 2 hrs. (e.g. no residual exotherm was observed using DSC). The Tg of the 90:10 package was better than the 80:20 package, so for further study we used the 90:10 package formulation. Table 4 Isothermal DSC (° C) Formulations Phr Cure schedule Onset Peak Residual Heat of rxn (J/g) Tg° C Time to 250K (mins) 98:2* MHHPA:BDMA 80 100C - 2 hrs 123 149 24.72 113 500 98:2* MHHPA:BDMA 80 150C -6 hrs NO NO NO 140C 500 90:10* MHHPA:A2910 30 100C-2h NO NO NO 61 833 90:10* MHHPA:A2910 40 100C-2h NO NO NO 89 795 90:10* MHHPA:A2910 50 100C-2h NO NO NO 99 845 90:10* MHHPA:A2910 60 100C-2h NO NO NO 103 905 = not inventive

The purpose of the next experiment was to determine the optimum ratio of epoxy to anhydride package. The results of DSC are shown in Table 4. The results show that optimum Tg and full conversion was obtained with the ratio of 100 part of epoxy: 60 part of anhydride package. The pot life was not significantly changed in spite of a higher ratio of accelerator to anhydride. In the traditional anhydride cure epoxy system, the accelerator is generally used between 1-4%. The Tg (°C) for different ratios of epoxy to anhydride (Phr) packages is shown in Fig. 1.

Dynamic DSC Example 5

The formulations described in the table below were mixed with bisphenol A diglycidyl ether resin (ratio of formulation to epoxy resin in range of 40-50g:100 g resin) using a stainless steel spatula until a uniform mixture was obtained. A 2 mg sample of this mixture was analyzed by using a commercially available DSC (TA Instruments QA20) having a software program embedded in the DSC that starts at 25°C and heats at 10°C/minute up to 300°C, cools and scans a second time to 250°C. The first scan provides cure data including onset temperature, peak exotherm and heat of reaction, while the second scan confirms the glass transition temperature. Table 5 Isothermal DSC (° C) Formulations Phr Cure schedule Onset Peak Heat of rxn Tg° C Time to 250K (mins) 90:3.6:6.4* MHHPA:AMI-1: octanoic acid 40 100C-2h 121 142 29 114 NO 90:3.6:6.4* MHHPA:AMI-1:octanoic acid 50 100C-2h 123 141 25 115 NO 95:1.8:3.2* MHHPA:AMI-1: octanoic acid 40 100C-2h 122 146 10 105 NO 95:1.8:3.2* MHHPA:AMI-1:octanoic acid 50 100C-2h 119 144 25 112 NO = not inventive
 Table 6 Isothermal DSC (° C) Formulations Phr Cure schedule Onset Peak Heat of rxn Tg° C Time to 250K (mins) 90:3.2:6.8* MHHPA: Non-sub-Imd:octanoic acid 40 100C-2h 124 144 8.9 J/g 121 NO 90:3.6:6.4* MHHPA:AMI-1:octanoic acid 50 100C-2h - - - 124 NO 95:1.6:3.4* MHHPA: Non-sub-Imd:octanoic acid 40 100C-2h 125 145 34.72 117 NO 95:1.6:3.4* MHHPA: Non-sub-Imd:octanoic acid 50 100C-2h 123 143 26.6 100 NO = not inventive
 Table 7 Mechanical Properties Formulation Phr Cure schedule Flexural Strength (psi) Flexural Modulus (ksi) ILLS (psi) 98:2 MHHPA:A2910* 80 150C for 6 hrs 160,604 6,342 7,738 90:10 MHHPA:A2910* 60 1 00C for 2 hrs 150,985 6,121 6,535 = not inventive

 A curing agent composition for epoxy resin comprising anhydride and approximately equimolar amount of tertiary amine or an imidazole and carboxylic acid wherein the weight ratio of anhydride to combined tertiary amine or imidazole and carboxylic acid is 50:50. A composition comprising the curing agent of claim 1 and epoxy resin. The composition of claim 2 where the epoxy to anhydride weight ratio is 1: 0.4 - 0.6. The composition of claim 3 wherein the temperature for curing the composition ranges from 80C to 100C for 1-2 hrs. The composition of claims 2-4 wherein the epoxy resin is a liquid epoxy resin or a multifunctional epoxy resin. The composition of claims 2-4 wherein the epoxy resin comprises at least one glycidyl ether selected from the group of glycidyl ethers of: resorcinol, hydroquinone, bis-(4-hydroxy-3,5-difluorophenyl)-methane, 1,1-bis-(4-hydroxyphenyl)-ethane, 2,2-bis-(4-hydroxy-3-methylphenyl)-propane, 2,2-bis-(4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis-(4-hydroxyphenyl)-propane, bis-(4-hydroxyphenyl)-methane, and combinations thereof. The curing composition of claims 1 wherein the anhydride is selected from the group consisting of methylhexahydrophthalic anhydride (MHHPA), nadic methyl anhydride (NMA), dodecenylsuccinic anhydride (DDSA), methyltetrahydrophthalic anhydride (MTHPA), hexahydrophthalic anhydride (HHPA). The composition of claims 2-6 further comprising an additive selected from the group consisting of epoxy tougheners, inorganic nano and micro fillers. Use of the composition set forth in any of claims 3-6 wherein the use is selected from the group consisting of adhesives and composite structural parts. The composition of claims 2-5 wherein the composition is made from a process selected from the group consisting of resin transfer molding (RTM), high pressure resin transfer molding (HP RTM), light resin transfer molding (LRTM), compression molding (CM), resin infusion, filament winding, casting, pultrusion, molding, and combinations thereof. The composition of claim 1 in which the tertiary amine or an imidazole in combination with a carboxylic acid is N-hydroxyethylpiperidine or an imidazole represented by the structure below: where R1 = H, a C1-C20 straight chain or branched alkyl, or a monocyclic aryl; and R2 = a C1-C20 straight chain or branched alkyl, or a monocyclic aryl. The composition of claim 11 wherein the carboxylic acid is represented by RCOOH; R = a C1-C20 straight chain or branched alkyl, or a monocyclic aryl. Härtungsmittelzusammensetzung für Epoxidharz, umfassend Anhydrid und eine ungefähr äquimolare Menge von tertiärem Amin oder einem Imidazol und Carbonsäure, wobei das Gewichtsverhältnis von Anhydrid zu kombiniertem tertiärem Amin oder Imidazol und Carbonsäure 50:50 beträgt. Zusammensetzung, umfassend das Härtungsmittel nach Anspruch 1 und Epoxidharz. Zusammensetzung nach Anspruch 2, wobei das Gewichtsverhältnis von Epoxid zu Anhydrid 1:0,4-0,6 beträgt. Zusammensetzung nach Anspruch 3, wobei die Temperatur für das Härten der Zusammensetzung im Bereich von 80 °C bis 100 °C über einen Zeitraum von 1 bis 2 h liegt. Zusammensetzung nach den Ansprüchen 2-4, wobei es sich bei dem Epoxidharz um ein flüssiges Epoxidharz oder ein multifunktionelles Epoxidharz handelt. Zusammensetzung nach den Ansprüchen 2-4, wobei das Epoxidharz mindestens einen Glycidylether umfasst, der aus der Gruppe der Glycidylether von Resorcin, Hydrochinon, Bis(4-hydroxy-3,5-difluorphenyl)-methan, 1,1-Bis(4-hydroxyphenyl)ethan, 2,2-Bis(4-hydroxy-3-methylphenyl)propan, 2,2-Bis(4-hydroxy-3,5-dichlorphenyl)propan, 2,2-Bis(4-hydroxyphenyl)propan, Bis(4-hydroxyphenyl)methan und Kombinationen davon ausgewählt ist. Härtungszusammensetzung nach Anspruch 1, wobei das Anhydrid aus der Gruppe bestehend aus Methylhexahydrophthalsäureanhydrid (MHHPA), Methyl-5-norbornen-2,3-dicarbonsäureanhydrid (Nadic Methyl Anhydride, NMA), Dodecenylbernsteinsäureanhydrid (DDSA), Methyltetrahydrophthalsäureanhydrid (MTHPA), Hexahydrophthalsäureanhydrid (HHPA) ausgewählt ist. Zusammensetzung nach den Ansprüchen 2 bis 6, ferner umfassend ein Additiv, das aus der Gruppe bestehend aus Epoxidharz-Zähigkeitsvermittlern, anorganischen Nano- und Mikrofüllstoffen ausgewählt ist. Verwendung der Zusammensetzung nach einem der Ansprüche 3-6, wobei die Verwendung aus der Gruppe bestehend aus Klebstoffen und Verbundbauteilen ausgewählt ist. Zusammensetzung nach den Ansprüchen 2-5, wobei die Zusammensetzung nach einem Verfahren hergestellt wird, das aus der Gruppe bestehend aus RTM (Resin Transfer Molding), HP-RTM (High Pressure Resin Transfer Molding), LRTM (Light Resin Transfer Molding), CM (Compression Molding), Harzinfusion, Fadenwickeln, Gießen, Pultrusion, Abformen und Kombinationen davon ausgewählt wird. Zusammensetzung nach Anspruch 1, wobei es sich bei dem tertiären Amin oder einem Imidazol in Kombination mit einer Carbonsäure um N-Hydroxyethylpiperidin oder ein durch die nachstehende Struktur wiedergegebenes Imidazol handelt: wobei R1 = H, ein geradkettiges oder verzweigtes C1-C20-Alkyl oder ein monocyclisches Aryl und R2 = ein geradkettiges oder verzweigtes C1-C20-Alkyl oder ein monocyclisches Aryl. Zusammensetzung nach Anspruch 11, wobei die Carbonsäure durch RCOOH wiedergegeben wird; R gleich ein geradkettiges oder verzweigtes C1-C20-Alkyl oder ein monocyclisches Aryl. Composition d'agent de durcissement pour de la résine époxy comprenant un anhydride et une quantité approximativement équimolaire d'une amine tertiaire ou d'un imidazole et d'un acide carboxylique dans laquelle le rapport pondéral de l'anhydride à l'amine tertiaire ou l'imidazole et l'acide carboxylique combinés est de 50:50. Composition comprenant l'agent de durcissement selon la revendication 1 et une résine époxy. Composition selon la revendication 2 où le rapport pondéral de l'époxy à l'anhydride est de 1:04-0,6. Composition selon la revendication 3 dans laquelle la température pour le durcissement de la composition va de 80 °C à 100 °C pendant 1-2 h. Composition selon les revendications 2-4 dans laquelle la résine époxy est une résine époxy liquide ou une résine époxy multifonctionnelle. Composition selon les revendications 2-4 dans laquelle la résine époxy comprend au moins un éther glycidylique choisi dans le groupe des éthers glycidyliques de : résorcinol, hydroquinone, bis (4-hydroxy-3,5-difluorophényl)méthane, 1,1-bis(4-hydroxyphényl)éthane, 2,2-bis(4-hydroxy-3-méthylphényl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophényl)propane, 2,2-bis(4-hydroxyphényl)propane, bis(4-hydroxyphényl)méthane et des combinaisons de ceux-ci. Composition de durcissement selon la revendication 1 dans laquelle l'anhydride est choisi dans le groupe constitué par l'anhydride méthylhexahydrophtalique (MHHPA), l'anhydride méthylnadique (NMA), l'anhydride dodécénylsuccinique (DDSA), l'anhydride méthyltétrahydrophtalique (MTHPA), l'anhydride hexahydrophtalique (HHPA). Composition selon les revendications 2-6 comprenant en outre un additif choisi dans le groupe constitué par les agents de renforcement d'époxy, les nanocharges et microcharges inorganiques. Utilisation de la composition exposée dans l'une quelconque des revendications 3-6 dans laquelle l'utilisation est choisie dans le groupe constitué par les adhésifs et les pièces de structure composites. Composition selon les revendications 2-5 dans laquelle la composition est formée à partir d'un procédé choisi dans le groupe constitué par le moulage par transfert de résine (RTM), le moulage par transfert de résine à haute pression (HP RTM), le moulage par transfert de résine sous vide (LRTM), le moulage par compression (CM), l'infusion de résine, l'enroulement filamentaire, la coulée, la pultrusion, le moulage et les combinaisons de ceux-ci. Composition selon la revendication 1 dans laquelle l'amine tertiaire ou un imidazole en combinaison avec un acide carboxylique est la N-hydroxyéthylpipéridine ou un imidazole représenté par la structure ci-dessous : où R1 = H, un alkyle en C1-C20 à chaîne droite ou ramifié ou un aryle monocyclique ; et R2 = un alkyle en C1-C20 à chaîne droite ou ramifié ou un aryle monocyclique. Composition selon la revendication 11 dans laquelle l'acide carboxylique est représenté par RCOOH ; R = un alkyle en C1-C20 à chaîne droite ou ramifié ou un aryle monocyclique.
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